/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 * RuleItem.java
 * Copyright (C) 2004 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.associations;

import weka.core.Instances;
import weka.core.RevisionHandler;
import weka.core.RevisionUtils;

import java.io.Serializable;
import java.util.Hashtable;

/**
 * Class for storing an (class) association rule. The premise and the
 * consequence are stored each as separate item sets. For every rule their
 * expected predictive accuracy and the time of generation is stored. These two
 * measures allow to introduce a sort order for rules.
 * 
 * @author Stefan Mutter
 * @version $Revision: 1.5 $
 */
public class RuleItem implements Comparable, Serializable, RevisionHandler {

	/** for serialization */
	private static final long serialVersionUID = -3761299128347476534L;

	/** The premise of a rule. */
	protected ItemSet m_premise;

	/** The consequence of a rule. */
	protected ItemSet m_consequence;

	/** The expected predictive accuracy of a rule. */
	protected double m_accuracy;

	/** The generation time of a rule. */
	protected int m_genTime;

	/**
	 * Constructor for an empty RuleItem
	 */
	public RuleItem() {

	}

	/**
	 * Constructor that generates a RuleItem out of a given one
	 * 
	 * @param toCopy
	 *            RuleItem to copy
	 */
	public RuleItem(RuleItem toCopy) {

		m_premise = toCopy.m_premise;
		m_consequence = toCopy.m_consequence;
		m_accuracy = toCopy.m_accuracy;
		m_genTime = toCopy.m_genTime;
	}

	/**
	 * Constructor
	 * 
	 * @param premise
	 *            the premise of the future RuleItem
	 * @param consequence
	 *            the consequence of the future RuleItem
	 * @param genTime
	 *            the time of generation of the future RuleItem
	 * @param ruleSupport
	 *            support of the rule
	 * @param m_midPoints
	 *            the mid poitns of the intervals
	 * @param m_priors
	 *            Hashtable containing the estimated prior probablilities
	 */
	public RuleItem(ItemSet premise, ItemSet consequence, int genTime,
			int ruleSupport, double[] m_midPoints, Hashtable m_priors) {

		m_premise = premise;
		m_consequence = consequence;
		m_accuracy = RuleGeneration.expectation((double) ruleSupport,
				m_premise.m_counter, m_midPoints, m_priors);
		// overflow, underflow
		if (Double.isNaN(m_accuracy) || m_accuracy < 0) {
			m_accuracy = Double.MIN_VALUE;
		}
		m_consequence.m_counter = ruleSupport;
		m_genTime = genTime;
	}

	/**
	 * Constructs a new RuleItem if the support of the given rule is above the
	 * support threshold.
	 * 
	 * @param premise
	 *            the premise
	 * @param consequence
	 *            the consequence
	 * @param instances
	 *            the instances
	 * @param genTime
	 *            the time of generation of the current premise and consequence
	 * @param minRuleCount
	 *            the support threshold
	 * @param m_midPoints
	 *            the mid points of the intervals
	 * @param m_priors
	 *            the estimated priori probabilities (in a hashtable)
	 * @return a RuleItem if its support is above the threshold, null otherwise
	 */
	public RuleItem generateRuleItem(ItemSet premise, ItemSet consequence,
			Instances instances, int genTime, int minRuleCount,
			double[] m_midPoints, Hashtable m_priors) {
		ItemSet rule = new ItemSet(instances.numInstances());
		rule.m_items = new int[(consequence.m_items).length];
		System.arraycopy(premise.m_items, 0, rule.m_items, 0,
				(premise.m_items).length);
		for (int k = 0; k < consequence.m_items.length; k++) {
			if (consequence.m_items[k] != -1)
				rule.m_items[k] = consequence.m_items[k];
		}
		for (int i = 0; i < instances.numInstances(); i++)
			rule.upDateCounter(instances.instance(i));
		int ruleSupport = rule.support();
		if (ruleSupport > minRuleCount) {
			RuleItem newRule = new RuleItem(premise, consequence, genTime,
					ruleSupport, m_midPoints, m_priors);
			return newRule;
		}
		return null;
	}

	// Note: this class has a natural ordering that is inconsistent with equals
	/**
	 * compares two RuleItems and allows an ordering concerning expected
	 * predictive accuracy and time of generation Note: this class has a natural
	 * ordering that is inconsistent with equals
	 * 
	 * @param o
	 *            RuleItem to compare
	 * @return integer indicating the sort oder of the two RuleItems
	 */
	public int compareTo(Object o) {

		if (this.m_accuracy == ((RuleItem) o).m_accuracy) {
			if ((this.m_genTime == ((RuleItem) o).m_genTime))
				return 0;
			if (this.m_genTime > ((RuleItem) o).m_genTime)
				return -1;
			if (this.m_genTime < ((RuleItem) o).m_genTime)
				return 1;
		}
		if (this.m_accuracy < ((RuleItem) o).m_accuracy)
			return -1;
		return 1;
	}

	/**
	 * returns whether two RuleItems are equal
	 * 
	 * @param o
	 *            RuleItem to compare
	 * @return true if the rules are equal, false otherwise
	 */
	public boolean equals(Object o) {

		if (o == null)
			return false;
		if (m_premise.equals(((RuleItem) o).m_premise)
				&& m_consequence.equals(((RuleItem) o).m_consequence))
			return true;
		return false;
	}

	/**
	 * Gets the expected predictive accuracy of a rule
	 * 
	 * @return the expected predictive accuracy of a rule stored as a RuleItem
	 */
	public double accuracy() {

		return m_accuracy;
	}

	/**
	 * Gets the premise of a rule
	 * 
	 * @return the premise of a rule stored as a RuleItem
	 */
	public ItemSet premise() {

		return m_premise;
	}

	/**
	 * Gets the consequence of a rule
	 * 
	 * @return the consequence of a rule stored as a RuleItem
	 */
	public ItemSet consequence() {

		return m_consequence;
	}

	/**
	 * Returns the revision string.
	 * 
	 * @return the revision
	 */
	public String getRevision() {
		return RevisionUtils.extract("$Revision: 1.5 $");
	}
}
